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Diffstat (limited to 'doc/gawk.texi')
| -rw-r--r-- | doc/gawk.texi | 64 |
1 files changed, 16 insertions, 48 deletions
diff --git a/doc/gawk.texi b/doc/gawk.texi index 1ad59242..17049b43 100644 --- a/doc/gawk.texi +++ b/doc/gawk.texi @@ -1056,7 +1056,6 @@ particular records in a file and perform operations upon them. * Extension New Mechanism Goals:: Goals for the new mechanism. * Extension Other Design Decisions:: Some other design decisions. * Extension Future Growth:: Some room for future growth. -* Old Extension Mechanism:: Some compatibility for old extensions. * Notes summary:: Summary of implementation notes. * Basic High Level:: The high level view. * Basic Data Typing:: A very quick intro to data types. @@ -5840,10 +5839,9 @@ range of the ASCII character set. Use a complemented character list in the ASCII range. @quotation NOTE -As of this writing (May 2018), Brian Kernighan's @command{awk} treats -@code{[:blank:]} like @code{[:space:]}, incorrectly matching -more characters than it should. We have submitted a patch to him, -and hope that this will be fixed. +Some older versions of Unix @command{awk} +treat @code{[:blank:]} like @code{[:space:]}, incorrectly matching +more characters than they should. Caveat Emptor. @end quotation @cindex bracket expressions, collating elements @@ -7123,6 +7121,8 @@ $ @kbd{echo a b c d e f | awk '@{ print "NF =", NF;} @quotation CAUTION Some versions of @command{awk} don't rebuild @code{$0} when @code{NF} is decremented. +Until August, 2018, this included BWK @command{awk}; fortunately +his version now handles this correctly. @end quotation Finally, there are times when it is convenient to force @@ -11073,6 +11073,9 @@ $ @kbd{gawk 'BEGIN @{ print "hello, \} @print{} hello, world @end example +In POSIX mode (@pxref{Options}), @command{gawk} does not +allow escaped newlines. Otherwise, it behaves as just described. + Brian Kernighan's @command{awk} and Busybox @command{awk} remove the backslash but leave the newline intact, as part of the string: @@ -11084,10 +11087,6 @@ $ @kbd{nawk 'BEGIN @{ print "hello, \} @print{} world @end example -In POSIX mode (@pxref{Options}), @command{gawk} does not -allow escaped newlines. Otherwise, it behaves as -just described. - @node Nondecimal-numbers @subsubsection Octal and Hexadecimal Numbers @cindex octal numbers @@ -19297,6 +19296,9 @@ The return values are summarized in @ref{table-system-return-values}. @end float @end table +As of August, 2018, BWK @command{awk} now follows @command{gawk}'s behavior +for the return value of @code{system()}. + @cindex sidebar, Controlling Output Buffering with @code{system()} @ifdocbook @docbook @@ -31996,7 +31998,7 @@ this looks something like the following: @example @group delta = 0.00001 # for example -difference = abs(a) - abs(b) # subtract the two values +difference = abs(a - b) # subtract the two values if (difference < delta) # all ok else @@ -32006,7 +32008,10 @@ else @noindent (We assume that you have a simple absolute value function named -@code{abs()} defined elsewhere in your program.) +@code{abs()} defined elsewhere in your program.) If you write a +function to compare values with a delta, you should be sure +to use @samp{difference < abs(delta)} in case someone passes +in a negative delta value. @node Errors accumulate @subsubsection Errors Accumulate @@ -40906,7 +40911,6 @@ maintainers of @command{gawk}. Everything in it applies specifically to * Future Extensions:: New features that may be implemented one day. * Implementation Limitations:: Some limitations of the implementation. * Extension Design:: Design notes about the extension API. -* Old Extension Mechanism:: Some compatibility for old extensions. * Notes summary:: Summary of implementation notes. @end menu @@ -41803,42 +41807,6 @@ conflicts. Of course, as of this writing, no decisions have been made with respect to any of the above. -@node Old Extension Mechanism -@appendixsec Compatibility For Old Extensions - -@ref{Dynamic Extensions}, describes the supported API and mechanisms -for writing extensions for @command{gawk}. This API was introduced -in @value{PVERSION} 4.1. However, for many years @command{gawk} -provided an extension mechanism that required knowledge of @command{gawk} -internals and that was not as well designed. - -In order to provide a transition period, @command{gawk} @value{PVERSION} 4.1 -continues to support the original extension mechanism. -This will be true for the life of exactly one major release. This support -will be withdrawn, and removed from the source code, at the next major -release. - -Briefly, original-style extensions should be compiled by including the -@file{awk.h} header file in the extension source code. Additionally, -you must define the identifier @samp{GAWK} when building (use -@samp{-DGAWK} with Unix-style compilers). Otherwise, the definitions -in @file{gawkapi.h} will cause conflicts with those in @file{awk.h} -and your extension will not compile. - -Just as in previous versions, you load an old-style extension with the -@code{extension()} built-in function (which is not otherwise documented). -This function in turn finds and loads the shared object file containing -the extension and calls its @code{dl_load()} C routine. - -Because original-style and new-style extensions use different initialization -routines (@code{dl_load()} versus @code{dlload()}), they may safely -be installed in the same directory (to be found by @env{AWKLIBPATH}) -without conflict. - -The @command{gawk} development team strongly recommends that you -convert any old extensions that you may have to use the new API -described in @ref{Dynamic Extensions}. - @node Notes summary @appendixsec Summary |